package name.jautzy.esi.server.util;

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

/**
 * Hex encoder and decoder.
 * 
 * @since 1.1
 * @author Apache Software Foundation
 * @version $Id: Hex.java,v 1.13 2004/04/18 18:22:33 ggregory Exp $
 */
class Hex {

  /**
   * Used building output as Hex
   */
  private static final char[] DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a',
      'b', 'c', 'd', 'e', 'f' };

  /**
   * Converts an array of characters representing hexidecimal values into an
   * array of bytes of those same values. The returned array will be half the
   * length of the passed array, as it takes two characters to represent any
   * given byte. An exception is thrown if the passed char array has an odd
   * number of elements.
   * 
   * @param data
   *          An array of characters containing hexidecimal digits
   * @return A byte array containing binary data decoded from the supplied char
   *         array.
   * @throws DecoderException
   *           Thrown if an odd number or illegal of characters is supplied
   */
  public static byte[] decodeHex(char[] data) throws RuntimeException {

    int len = data.length;

    if ((len & 0x01) != 0) {
      throw new RuntimeException("Odd number of characters.");
    }

    byte[] out = new byte[len >> 1];

    // two characters form the hex value.
    for (int i = 0, j = 0; j < len; i++) {
      int f = toDigit(data[j], j) << 4;
      j++;
      f = f | toDigit(data[j], j);
      j++;
      out[i] = (byte) (f & 0xFF);
    }

    return out;
  }

  /**
   * Converts a hexadecimal character to an integer.
   * 
   * @param ch
   *          A character to convert to an integer digit
   * @param index
   *          The index of the character in the source
   * @return An integer
   * @throws DecoderException
   *           Thrown if ch is an illegal hex character
   */
  protected static int toDigit(char ch, int index) throws RuntimeException {
    int digit = Character.digit(ch, 16);
    if (digit == -1) {
      throw new RuntimeException("Illegal hexadecimal charcter " + ch + " at index " + index);
    }
    return digit;
  }

  /**
   * Converts an array of bytes into an array of characters representing the
   * hexidecimal values of each byte in order. The returned array will be double
   * the length of the passed array, as it takes two characters to represent any
   * given byte.
   * 
   * @param data
   *          a byte[] to convert to Hex characters
   * @return A char[] containing hexidecimal characters
   */
  public static char[] encodeHex(byte[] data) {

    int l = data.length;

    char[] out = new char[l << 1];

    // two characters form the hex value.
    for (int i = 0, j = 0; i < l; i++) {
      out[j++] = DIGITS[(0xF0 & data[i]) >>> 4];
      out[j++] = DIGITS[0x0F & data[i]];
    }

    return out;
  }

  /**
   * Converts an array of character bytes representing hexidecimal values into
   * an array of bytes of those same values. The returned array will be half the
   * length of the passed array, as it takes two characters to represent any
   * given byte. An exception is thrown if the passed char array has an odd
   * number of elements.
   * 
   * @param array
   *          An array of character bytes containing hexidecimal digits
   * @return A byte array containing binary data decoded from the supplied byte
   *         array (representing characters).
   * @throws DecoderException
   *           Thrown if an odd number of characters is supplied to this
   *           function
   * @see #decodeHex(char[])
   */
  public byte[] decode(byte[] array) throws RuntimeException {
    return decodeHex(new String(array).toCharArray());
  }

  /**
   * Converts a String or an array of character bytes representing hexidecimal
   * values into an array of bytes of those same values. The returned array will
   * be half the length of the passed String or array, as it takes two
   * characters to represent any given byte. An exception is thrown if the
   * passed char array has an odd number of elements.
   * 
   * @param object
   *          A String or, an array of character bytes containing hexidecimal
   *          digits
   * @return A byte array containing binary data decoded from the supplied byte
   *         array (representing characters).
   * @throws DecoderException
   *           Thrown if an odd number of characters is supplied to this
   *           function or the object is not a String or char[]
   * @see #decodeHex(char[])
   */
  public Object decode(Object object) throws RuntimeException {
    try {
      char[] charArray = object instanceof String ? ((String) object).toCharArray()
          : (char[]) object;
      return decodeHex(charArray);
    } catch (ClassCastException e) {
      throw new RuntimeException(e.getMessage());
    }
  }

  /**
   * Converts an array of bytes into an array of bytes for the characters
   * representing the hexidecimal values of each byte in order. The returned
   * array will be double the length of the passed array, as it takes two
   * characters to represent any given byte.
   * 
   * @param array
   *          a byte[] to convert to Hex characters
   * @return A byte[] containing the bytes of the hexidecimal characters
   * @see #encodeHex(byte[])
   */
  public byte[] encode(byte[] array) {
    return new String(encodeHex(array)).getBytes();
  }

  /**
   * Converts a String or an array of bytes into an array of characters
   * representing the hexidecimal values of each byte in order. The returned
   * array will be double the length of the passed String or array, as it takes
   * two characters to represent any given byte.
   * 
   * @param object
   *          a String, or byte[] to convert to Hex characters
   * @return A char[] containing hexidecimal characters
   * @throws EncoderException
   *           Thrown if the given object is not a String or byte[]
   * @see #encodeHex(byte[])
   */
  public Object encode(Object object) throws Exception {
    try {
      byte[] byteArray = object instanceof String ? ((String) object).getBytes() : (byte[]) object;
      return encodeHex(byteArray);
    } catch (ClassCastException e) {
      throw new RuntimeException(e.getMessage());
    }
  }

}
